Games that you might enjoy:
Resistance and Resistance 2 (if your into FPS), Motorstorm and Motorstorm Pacific Rift, Wipeout HD (PSN download), Ratchet and Clank Tools of Destruction, Ratchet and Clank Quest for Booty (PSN Download), Warhawk (Online only), Disgaea 3 (Out next spring in EU), Valkyria Chronicles (Fantastic game but unfortunately the hidden gem of this christmas), Mirror's Edge (imo), Eye of Judgment (If your into trading card games, includes Playstation Eye), MGS4, Devil May Cry 4, Heavenly Sword, Super Stardust HD (PSN download), GH3/GHWT/RB/RB2 (whatever you prefer), Folklore, Burnout Paradise, Uncharted (This one is an absolute must!!!).
Definitely get LittleBigPlanet!!!!
Accessories:
Playstation Eye (See above), Extra Controllers, and just in case, you might want to pick up an extra 2.5 SATA hard drive as you can replace the 80gb that comes with the console with say 320gb, there are tutorials on how to do this on IGN and even a video demonstration somewhere on Gametrailers.
Things to know:
The service for Playstation network is free to join, the only payments you'll need to do are with download content and in rare cases extra themes for the XMB (IE; Megaman 9 themes). The firmware updates can take a while but that's ok, you have an internet browser on the XMB available and no need for an extra stuff like a wireless attachment because the PS3 has wireless built in. I use my BT hub as the router for my PS3 and it works fantastically.
Oh yes, you can also download PSP games on your PS3 now and if you like importing things from other countries, the games are region free as are some blu ray movies (Example, Hellboy).
Anything else that can be added onto this?